add the cmd/tools/gen_1long_fn.v script too

cmd/tools/gen_1long_fn.v

@@ -0,0 +1,15 @@
+import strings
+import os
+
+n := os.args[1] or { '1_000_000' }.int()
+stmt := os.args[2] or { 'a = b + c * d' }
+
+mut s := strings.new_builder(1000)
+s.writeln('fn main() {')
+s.writeln('    mut a,b,c,d := 0,1,2,3')
+for _ in 0 .. n {
+	s.writeln('    ${stmt}')
+}
+s.writeln('    println("a: \${a}")')
+s.writeln('}')
+os.write_file('${n}.v', s.str())!